ACTION POTENTIAL Flashcards
regular motor neuron
- 2 msec immediate reaction e.g. in boxing
skeletal muscle motor neuron
- 5 msec immediate reaction eg in boxing
cardiac ventricle action potential
- 200 msec
- due to blood to flow and eject
potassium leave the cell negative also with
- chloride because it is also negative
action potential predominantly related to
- Na influx
tetrodotoxin
- paralyzed positive and negative charges in neuron muscular junction
- freeze neural transmission
- no depolarization
too much repolarization will cause
- hyperpolarization
sub threshold potential change
- proportional stimulus
- not propagated but decremental with distance
- EXHIBITS SUMMATION (multiple stimulus)
action potential
- independent of stimulus
- propagated unchanged in magnitude
- SUMMATION NOT POSSIBLE
- DOWNHILL
ungated
- continous
- based on concentration gradient
- not affected by action potential
- not based on charge
- not affected by gradient
voltage gated channels
- create the concentration difference
- not continuous
- affected by action potential
conductance
- ions in and out of the cell
depolarization
- opening of voltage-gated Na channels
repolarization
- voltage gated Na channel are rapidly closing
- voltage gated K are still opening increasing K+ conductance
- Na/K-ATPase pump
major conductance of K
- out of the cell
- efflux
major conductance of Na
- into the cell
- influx
neural tissue that is equal outside and equal inside/ steady state
- dead tissue
Na goes IN (+)
- the voltage becomes more positive of the interior of the cell
- depolarization
absolute refractory period
- functional refractory period
- no matter how strong the stimulus it cannot induce as second action potential
- due to voltage inactivation of SODIUM channels
- actual depolarization and repolarization
relative refractory period
- greater than normal stimulus is required to induce a second action potential
- hyper polarized then preparing for repolarization
Na channel closed
- stop depolarizing
K leaves the cell
- depolarized back to normal
K continous to leave
- hyperpolarization
important factors of action potential
- size of the action potential
- cell diameter
- myelination- insulation conduct more lose a lot of energy, more conduction
- demyelination
neuromuscular junction released
- calcium released Ach
- Ach makes action potential at the neuromuscular junction
- sodium goes in
- potassium goes out
ligand
- special protein
neuromuscular transmission
action potential travels down to
axon
ends in the presynaptic motor axon terminal
opens voltage-gated calcium channels
2 part
increase in Ca2+ permeability of the axon terminal
causes influx of extracellular Ca2+
into the axon terminal
3rd part
rise in intracellular free Ca2+ causes release of Ach
from synaptic vesicles
into the synaptic cleft
4th part
diffusion of Ach to post junctional membrane
5th part
combination of Ach with cholinergic nicotinic receptor on the post junctional membrane
6th part
opening of ligand dependent channels
result in increased conductance to Na+ and K+
7th part
influx of Na+ causes local depolarization of post junctional membrane
8th part
EPP (end plate potential) spreads
causing depolarization of areas of muscle membrane adjacent to end plate
more myelin and thicker axons
- faster the conductance
vesicles release
- Ach
transmitter that generate EPSP (excitatory)
- Ach- excitatory
- glutamate- stimulatory
- aspartate- stimulatory
transmitter that generate IPSP (inhibitory) produced by increase conductance to Cl- into the cell
- glycine
- GABA
myasthenia gravis
- disease in the neuromuscular junction
- defect of Ach receptor
- ssx double vision
- difficulty chewing
